Centralized traffic controlling system for railroads



June 28, 1938.

Pied,

D. F. DE LONG.

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS End Field Siafion Fir-5f. Field Sfcdion Conl'rcl Office Filed July 25, 1934 4 Sheets-Sheet l M @Ma ATTORN EY June 28, 1938. D. F. D: LONG CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Jqly 25, 1934 4 Sheets-Sheet 2 ATTORNEY June 28, 1938. D. F. DE LONG CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed July 25, 1934 4 Sheets-Sheet 3 8% NE :sw Eu T R :p(,

ATTORNEY June 28, 1938.

D. F. DE LONG CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Fild July 25, 1934 4 Sheets-Sheet 4 ATTORNiEY Jllllll Patented June 28, 1938 UNITE CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS ter, N. Y.

Application July 25, 1934, Serial No. 736,949

13 Claims.

This invention relates to centralized traific controlling systems for railroads and it more par- 'ticularly pertains to the communication part of such systems.

The present invention contemplates a centralized trafiic controlling system in which communication is established between a central control office and a large number of outlying field stations by means of a communication system of the selective coded simplex type. The switches and signals at a plurality of stations located along the railroad track are connected to the control office by means of a two-wire line circuit.

The switches and signals are under the supervision of the operator at the control oflice so that the condition of such switches, signals and various other traflic controlling devices at the distant stations will be transmitted to the control ofiice for providing the operator with the necessary information for governing train movements. In a system of this type a series of impulses forming a particular code combination is transmitted over the line circuit for the selection of a particular field station and the transmission of controls to the selected station. Similarly, a series of impulses forming a particular code combination is transmitted over the line circuit for the registration of a field station in the control office and the transmission of indications from the registered station. The control circuits and the indication circuits are so interrelated in the system employed that controls and indications are transmitted on separate cycles of operation.

It is proposed to provide a line battery at the control ofiice with a mid-tap connected to one line conductor and with the opposite terminals of the battery selectively connected to the other line conductor.

Either control impulses are transmitted from the control ofiice or indication impulses are transmitted from a field station during any particular operating. cycle. The control impulses are made distinctive by reason of their polarity for the purpose of transmitting the desired control code combination. The indication impulses are made distinctive by reason of the strength of current in the line circuit for each impulse and also by reason of the length of time during which the line circuit is energized for each impulse. Therefore the capacity of the system of the present invention for the transmission of indications is double that for the transmission of controls.

The system is so organized that irrespective of the simultaneous occurrence of controls and indications to be transmitted only one location is effective to transmit impulses at any one time. For example, the control office may transmit control impulses over the line circuit during an operating cycle and during this cycle all field stations are prevented from obtaining access to the communication circuit for transmitting indication impulses. Likewise, when one of the field stations is transmitting impulses to the control ofiice all other field stations are locked out and the circuits are arranged to guard against the control office breaking in on the line during an indication cycle. If there are several stored controls and indications awaiting transmission at the end of an operating cycle, the control office is given preference and the system functions to transmit all of the waiting controls before a field station can obtain access to the line for transmitting in-' dications.

The polarity of the impulses during the transmission of controls is determined in the control office by selectively connecting the line battery to the line circuit. For a control cycle the impulses are all of comparativelyshort (normal) length and comparatively weak (normal) strength. The impulses during the transmission of indications are of the same polarity, but are varied in length and in the strength of current in accordance with the code combination made up at the transmitting field station. In otherwords the field station which is transmitting its indications is capable of selectively applying any one of four different conditions to the line circuit during each step. These four conditions are, first, negative, short, strong impulse; second, negative, short, weak impulse; third, negative, long, strong impulse, and fourth, negative, long, weak impulse. The control oflice in transmitting controls is capable of selecting only one of two difierent conditions to be applied to the line circuit for each step, these conditions being and These characteristic features of the present invention will be explained more in detail in the following description of one embodiment and various other characteristic features, advantages and functions of the invention will be in part pointed out and in part apparent as the description progresses.

In describing the invention in detail reference will be made to the accompanying drawings which illustrate one method of carrying out the invention by way of example. The drawings illustrate, in a diagrammatic manner. the apparatus and circuits employed and for convenience in describing the invention in detail those parts having similar features and functions are designated in the various views by like letter reference characters, generally made distinctive either by reason of distinctive exponents representative of their location or by reason of preceding numerals representative of the order of their operation and in which:

Fig. 1 illustrates, in schematic form, the twowire line circuit extending from the control office, through a first field station to the end field station, with certain contacts and relays illustrated to show the fundamental control of the line circuit.

Figs. 2A and 23 (with Fig. 2B placed below Fig. 2A) illustrate the apparatus and circuit arrangements employed at a typical control office embodying the present invention.

Fig. 3 illustrates the apparatus and circuit arrangement employed at a typical field station embodying the present invention.

The illustrations in the drawings are. schematic and abbreviated for the purpose of clearness and simplicity. The detailed operation of the circuits may be conveniently followed by placing Fig. 3 to the right of Fig. 2A and by placing Fig. 2B below Fig. 2A, with correspondingly numbered lines in alinement.

The arrangement of those parts of the system which are not illustrated in the drawings and their cooperation and connection with the illustrated portions will be set forth in the following general description. After the general description, a detailed description will be given of the transmission of controls from the control of-- fice for selecting a field station and for operating-control devices thereat. Likewise, a detailed description will be given of the transmission of indications from a field station for registering such station in the control ofiice and for there after selectively operating indication devices associated with the registered station in the control office.

General description The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of direct current and the circuits with which these symbols are used always have current flowing in the same direction. The symbols (3+) and (3-) indicate connections to the opposite terminals of a suitable battery or other direct current source, which has an intermediate or mid-tap (CN) and the circuits with which these circuits are used may have current flowing in one direction or the other depending upon the particular terminal used in combination with tap (CN).

For convenience in describing the operation of the system, the two line wires connecting the control oifice with the stations are identified by referring to them as the stepping line and the return line. The stepping line is the line in which the line relays at the office and at the field stations are connected, as well as the impulsing contacts of the impulsing relay located in the control ofiice. This line conductor also contains other contacts for starting purposes, the details of which will be explained later. The stepping line and the return line extend in series through all of the field stations and are tied together at the end station.

In considering the organization of the line circuit illustrated in Fig. 1 it will be understood that additional field stations may be connected in the line between the control oiiice and the first field station or between the first field station and the end field station.

Control ojfice equipment-The control ofiice (see Figs. 2A and 213) includes a quick acting line relay F of the polar biased-to-neutral type, which has its contacts positioned to the right when a impulse is connected to the stepping line in the control oifice and to the left when a impulse is connected to the stepping line in the control office. A marginal line relay HL of the neutral type is connected in series with line relay F in the stepping line, this relay having such a value and adjustment that it is not picked up when current is flowing over the line circuit with resistance unit R. at the field station in circuit. Relay BL is picked up when resistance unit R is short circuited, to provide a substantial increase in current fiow in the line circuit. In other words relay HL responds to a strong impulse but not to a weak impulse.

A quick acting line repeating relay FP repeats each energization of the line relay F, irrespective of the polarity which energizes relay F. Slow acting relays SA and SAP are picked up in sequence at the beginning of each cycleand are dropped in sequence at the end of each cycle. Relay SA has such slow acting characteristics that it does not drop away between successive energizations of relay FP and consequently relays SA and SAP do not drop away during impulsing.

The impulses of a cycle of operations cause the step-by-step operation of a stepping relay bank, including relays 'IV, 2V, 3V, 4V, LV and VP. Thisstepping bank is arranged to take one step for each de-energized period of the line circuit between impulses. In other. words the stepping relays are picked up one at a time during each off period. The half step relay VP shifts its position during each on period. In this description the de-energized period of the line circuit is conveniently referred to as the off period and the energized period of the line circuit is conveniently referred to as the on period.

Impulsing relay E is controlled by the stepping relay bank in such a way that it time spaces the impulses in the line circuit in accordance with the actual response of the stepping bank. Impulse repeating relay EP' is provided to measure the length of the impulses in the line circuit and thus functions toregister the two indication conditions provided by the short and long impulse periods of the system.

Starting relay STR is picked up at the start of each control cycle and dropped at the end of each control cycle. Relay STR remains down during an indication cycle. Checking relay CK is picked up at the beginning of a control cycle and is dropped at the end of a control cycle. Control relay C is momentarily picked up at the beginning of both control and indication cycles. The detailed operations of these relays will be pointed out later in the description.

Polarity control relay D is of the polar magnetic stick type and is for the purpose of selectively connecting the line battery LB to the line circuit during the off periods, in preparationfor energizing the line circuit with the proper polarity during the succeeding on periods. Code determining relay CD is one of a bank of such relays which are so interconnected that the momentary depression of a starting button, such as SB, causes relay CD to be picked up for initiating the system into a control cycle. The

interconnection of the CD relays and the storing relays (not shown), which function to store the operations of the starting buttons and to permit only one CD relay to be picked up at any one time is immaterial to an understanding of the present invention, although this feature has been completely disclosed in the prior application of N. D. Preston et al. Ser. No. 455,304 filed May 24, 1930, corresponding to Australian Patent 1,501 of 1931.

As typical of the control levers located in the control ofiice, switch machine lever SML is shown. This lever is for the purpose of governing the track switch at the station corresponding to relay CD. It will be understood that additional levers for controlling the signals at the stations will be provided, but it is not believed necessary to complicate the drawings by showing this ad ditional equipment, since the operation controlled by lever SML is typical of the operations controlled by additional levers.

For the purpose of illustrating station registration, a typical pilot arrangement is shown in Fig. 23. Pilot relays IPT and ZPT are positioned on the first step of the cycle in accordance with the indications transmitted. Relay IPT is controlled over the length of time indication bus LTI and relay ZPT is controlled over the strength of current indication bus SCI. It will be understood that additional pilot relays may be provided and connected on additional steps, up to the point where suflicient codes for station registration are obtained. Since bus LTI can be conditioned in either one of twoways and since bus SCI can be conditioned in either one of two ways, four different conditions for each step are obtained. These four conditions position relays lPT and ZPT in their four difierent combinations.

Station relay IST is for the purpose of registering the station which positions relays IPT and ZPT to the left on the first step. This relay is merely typical of a number of such relays which would ordinarily be provided, one for registering each individual station. Additional station relays would be connected to additional contacts of the pilot relays in their various combinations.

Suitable indication storing relays such as IIR and 21R are for storing the variousindications from a registered field station, after such a station has been registered in the control ofiice by the energization of its station relay. It will be understood that relays HR and HR are merely typical of a number of such indication storing relays which may be provided for storing all of the indications transmitted from a registered field station and that the contacts of these indication storing relays may be connected to lamps or other indicating devices.

Field station equipment.-The field station i1- lustrated in Fig. 3 includes a quick acting line relay F of the biased-to-neutral polar type, actuated to the right by impulses applied to the line circuit and to the left by impulses. Quick acting line repeating relay FP of the neutral type repeats the impulses in the line circuit, irrespective of their polarities. Slow acting relays SA and SAP correspond to similar relays in the control office and are used to define the bounds of an operating cycle, since they are picked up at the beginning of each cycle and dropped at the end of each cycle.

Checking relay CK corresponds to the similar relay in the control office and is picked up at the beginning of a control cycle and released at the end of a control cycle, but is not picked up during an indication cycle. The field station includes a lookout relay LO which is picked up at the station which is sending indications. As will be later described, the circuits of this lookout relay are so organized that the station nearest the control ofiice obtains access to the communication system when several stations have simultaneous indications ready to transmit and other stations are locked out.

Relay HL is the relay at the station for varying the current in the line circuit to provide a choice of two conditions, by determining whether the current in the line shall be strong or weak in character. This relay is controlled on the various steps of a cycle over the strength of current indication bus SCI Relay P is provided for determining the length of time during which the line circuit shall be energized for providing the additional choice of two conditions, that is, short and long impulses of current. This relay is controlled on the various steps of a cycle over the length of time indication bus LTI Impulse relay PL is for the purpose of impulsing the line circuit during the transmission of indications.

A stepping relay bank including relays lv 2V 3V 4V and VP is provided which operates in synchronism with the corresponding relay bank in the control ofiice, so that they take one step for each off period for marking off the steps of the cycle. Pilot relay IPT is controlled over control bus C'I'L on the first step of the cycle in accordance with the polarity of the first impulse. On the second step of the cycle, switch machine control relay SMR is controlled in accordance with the polarity of the second imipulse at the station selected by the pilot relay. It will be understood that additional pilot relays and additional control relays may be provided and connected in an obvious manner as the size of the system demands.

Track switch TS is operated by switch machine SM in accordance with the impulse received over the line circuit which positions switch machine relay SMR The position and .the locked and unlocked conditions of the track switch are repeated by the usual switch repeating relay WP This switch repeating relay picks up its neutral contact when the associated track switch is in either of its locked positions and drops this contact when the switch machineis unlocked. The polar contacts of this relay are assumed to be positioned to the right when the associated track switch is in its normal position and to the left when the switch is in reverse.

The polar contacts of relay WP are shown for the purpose of indicating on the drawings that this is the usual track switch polar repeater relay. The polar contacts of this relay may connect to indication channel circuits connected to front contacts of the stepping relays, such as contacts I53 and E63 for example, for transmitting indications representing the position of the track switch. Since these additional indications will be transmitted in a similar manner to other typical indications controlled by back contacts I55 and IE6 of relays T and WP, it is believed unnecessary to illustrate or explain the circuits in detail.

Suitable signals are also provided (not shown) for governing trafiic over the track section illustrated in Fig. 3 and their control is in accordance with suitable automatic signalling, in cooperation with manual signalling controlled over the communication system. Since this signal control is accomplished on the various steps of the cycle in a'manner similar to that shown for controlling the switch machine operation, it is not believed necessary to show this portion of the system.

Track relay T registers a change in the condition of the detector track section with which this relay is associated. It is energized when the track section is unoccupied and de-energized when the track section is occupied. Change relay OH is the relay which registers the change in condition of any of the devices at the associated station, which requires that the communication system transmit indications to the control ofiice. Although the circuit of relay CH is not shown it will be understood that it is normally energized and when relay WP or relay T change positions, the circuit of relay CH is momentarily interrupted so that it is de-energized to initiate an indication cycle.

The detail operation relating to the manner in which relay CH is controlled to store indications for transmission on a subsequent cycle when the line is in use, is explained in detail in De Long et al., Patent No. 1,852,402, issued April 5, 1932. Relay CH of Fig. 3 is assumed to be operated in the same way that relay CH of this De Long patent is operated.

It is believed that the nature of the invention, its advantages and characteristic features may be best understood by continuing the description in a manner relating to the detailed operation of the system.

Operation With the system in its normal or period of blank condition, the line circuit is normally energized with potential applied to line i I which positions all of the line relays to the left. The current flow under this condition. is of a comparatively low value since all of the station line relays are connected in series and resistance R at the end station is in the circuit. When a station obtains access to the line for transmitting its indications, a resistance unit is connected in the line circuit for maintaining the current flow at this comparatively low value and during the transmission .of indications this current flow can be increased in Value by short circuiting the resistance unit.

A cycle of operations for the transmission of controls is started by initially, momentarily changing the energization of the line circuit to a energization. A cycle of operations for the transmission of indications is started by initially de-energizing the line circuit, all of which will be explained in detail.

Normal at rest conditions.The line circuit is normally energized from the terminal of line battery LB, contact 20 of relay D in its left hand position, windings of relays F and HL, back contact 2! of relay C, front contact 22 of relay EP, back contact 23 of relay E, line conductor ll, winding of relay F back contact mt of relay L and through the other stations in series, in cluding the tie and resistance R at the end station and line conductor 10 to the mid-tap of battery LB.

Relay D in the control oflice is normally positioned to the left by means of a circuit extending from (B-), back contact 24 of relay STR and winding of relay D to (CN). Relay EP is normally energized over a circuit extending from back contact 25 of relay E and winding of relay EP to Since relay F has its contacts normally positioned to the left, a circuit is completed for normally energizing relay FP which extends from contact 26 of relay F in its left hand position and winding of relay FP to At the field station in addition to relays WP T and CH being normally energized as above mentioned, relay FP is normally energized over a circuit extending from contact i2! of relay F in its left hand position and winding of relay FP to Manual start.With the system in its normal condition, the operator can initiate a cycle for the selection of a particular station and the transmission of controls to that station. For example, if he desires to operate track switch TS from its normal to its reverse position he moves the switch machine lever SML from its normal to its reverse position and then actuates starting button SE. The actuation of button SB while the system is at rest causes the energization of relay CD. Relay CD closes a circuit for picking up relay STR which extends from back contact l2 of relay SA, lower winding of relay STR and front contact 2'! of relay CD to The actuation of relay STR closes a circuit for actuating relay D to the right which extends from B+, back contacts 30, 3|, 32, 33 and 34 of relays l V, 2V, 3V, 4V and LV respectively, control bus CTL, front contact 24 of relay STR and winding of relay D to (CN). The shifting of contact 20 of relay D changes the energization of stepping line conductor II from to which marks the beginning of the initiating period. Therefore all line relays will be actuated to their right hand positions. During this change in the positions of the line relay contacts, the associated FP relays are momentarily deenergized but this operation is of no effect.

A circuit is now closed for picking up checking relay CK which extends from (B+) contact 28 of relay Fin its right hand dotted position, back contact 29 of relay SA and upper winding of relay OK to (ON). Relay CK closes a stick circuit for itself extending from front contact and lower winding of relay OK to It will be noted that the energizing circuits of the two windings of relay CK are in a direction to energize both of these windings in aiding relation, as indicated by the arrows associated with these windings. Relay CK remains picked up throughout a control cycle and at its front contact 96 connects to the winding of relay EP for maintaining thisrelay energized during such a cycle. Relay CK closes a stick circuit for relay STR extending from front contacts 91 and 98 of relays CK and STR respectively, upper winding of relay STR and back contact 5! of relay LV to A circuit is now closed for picking up relay C which extends from front contact 35 of relay FP, front contact 36 of relay CK, back contact 31 of relay SAP, back contact 38 of relay SA and winding of relay C to Relay 0 closes a stick circuit for itself extending from back contact 39 of relay SAP, front contact 59 and winding of relay C to Relay C opens its back contact 2| which deenergizes the line to mark the beginning of the conditioning oif period. The momentary energization of the line circuit just described is the initiating period. During this initiating period the shifting of relay F at the field station to its right hand position closes a circuit for picking up relay CK extending from (B+), contact I22 of relay F in its right hand dotted position, back contact I23 of relay SA and upper winding of relay CK to (CN) Relay K closes a stick circuit for itself extending from front contact I 24 and lower winding of relay 0K to The energization of both windings of relay CK is such that these windings aid as indicated by the arrows. The pick-up of relay CK opens the circuit of relay LO at back contact I4! so that the field station cannot obtain access to the system after it has been initiated by the control office.

When relay F is de-energized at the beginning of the conditioning off period, the opening of its contact 26 de-energizes relay FP which closes a circuit for picking up relay SA extending from back contact 40 of relay FP, back contact II of relay SAP and winding of relay SA to During the following impulses of the cycle, relay SA is energized at each on period over a circuit extending from front contact 40 of relay FP, front contact 42 and Winding of relay SA to so that relay SA closes a circuit for picking up relay SAP which extends from front contact 43 of relay SA and winding of relay SAP to The opening of back contact 38 of relay SA and back contact 39 of relay SAP deenergizes the pick-up and stick circuits of relay C so that this relay drops its contacts. This closes the line at back contact 2| to mark the beginning of the first on period.

At-the field station, relay SA is picked up when relay FP is dropped during the conditioning period over a circuit extending from back contact I25 of relay FP back contact I26 of relay SAP and winding of relay SA to Relay SA remains picked up during the cycle over a circuit including front contact I25 of relay PP and front contact I21 of relay SA Relay SA closes a circuit for picking up relay SAP which extends from front contact I28 of relay SA and winding of relay SAP to It will be understood that the same operation takes place at all other field stations connected to the line circuit as described in connection with the typical field station illustrated in Fig. 3. The energization of the line circuit during a control cycle is of comparatively low current value due to the resistance unit R included in the line circuit at the end station and since no field station can condition the line by changing its resistance during the on periods of a control cycle, relay H11 in the control oflice remains ole-energized. In addition to this, the executing circuit controlled by relay I-IL, including bus SCI, is opened at back contact 50 of relay CK to prevent the energization of the individual indication circuits selected by the stepping relay bank in the control office.

Line impulsing and stepping relay operation. Although the description of the stepping and impulsing operations will be more particularly directedto Fig. 2A, it will be understood that similar operations take place at the field station illustrated in Fig. 3 and at other stations along the line. Contacts H2, H3 and H4 of relays SA and PP correspond to contacts I2, I3 and I I of relays SA and PP in the control office. With the understanding that stepping occurs at the field stations in synchronism with stepping in the control oflice it is believed unnecessary to describe this operation in detail at the field stations.

After relay SA picks up in the conditioning off period, a circuit is closed for picking up relay IV extending from front contact I2- of relay SA, back contact I3 of relay FP, back con-- tact I! of relay VP, back contacts I8 and 58 of relay IV to Relay IV closes a stick circuit for itself extending from front contact I2 of relay SA, front contact 5'! and winding of relay IV to When relay FP picks up at the beginning of the first on period, a circuit is closed for picking up relay VP which extends from (3+) front contact 44 of relay IV, back contacts 85, 45 and ll of relays 2V, 3V and 4V respectively, lower winding of relay VP and front contact Id of relay FP'to (CN) Relay VP closes a stick circuit for itself extending from front contact I2 of relay SA, front contact 52 and upper winding of relay VP to A circuit is closed for picking up relay E which extends from front contact 48 of relay CK, back contacts 50, 5! and 62 of relays 4V, 3V and 2V respectively, front contact 63 of relay IV, front contact lit of relay VP and upper winding of relay E to The opening of back contact 23 of relay E de-energizes the line circuit, since back contact I3 of relay CK in bridge of contact 23 now open.

This marks the beginning of the first off period which results in dropping relay FP. A circuit is now closed for picking up relay 2V which extends from front contact I2 of relay SA, 1

back contact I3 of relay FP, front contact ll of relay VP, back contact I9 of relay 3V, front contact 59 of relay. IV and winding of relay 2V to Relay 2V closes an obvious stick circuit for itself at its front contact 56. The opening of back contact 62 of relay 2V de-energizes relay E and when its back contact 23 is closed the line circuit is again energized.

This marks the beginning of the second on period which picks up relay FP. Relay VP is now de-energized by means of a circuit extending from (B-), front contact ll] of relay VP, front contact 45 of relay 2V, back contacts 46 and 4'! of relays 3V and 2V, lower winding of relay VP and front contact Id of relay HP to (CN). Current over this circuit through the lower winding of VP flows in opposite direction to the above described stick circuit through the upper winding, so that the two windings now oppose with the result that relay VP drops its contacts. Relay E is now picked up over a circuit extending from front contact 48 of relay CK, back contacts 60 and SI of relays 4V and 3V respectively, front contact 52 of relay 2V, back contact 65 of relay VP and lower winding of relay E to The opening of contact 23 of relay E de-energizes the line circuit.

This marks the beginning of the second off period which drops relay FP. A circuit is now closed for picking up relay 3V extending from front contact I2 of relay SA, back contacts I3, I! and I8 of relays FP, VP and 4V respectively, front contact 58 of relay 2V and winding of relay 3V to Relay 3V closes an obvious stick circuit for itself at its front contact 55. is now de-energized because the previously described energizing circuit through the-lower winding of this relay is open at back contact SI of relay 3V. The closing of back contact 23 of relay E energizes the line circuit.

This marks the beginning of the third on period which picks up relay FP. A circuit is nowclosed for picking up relay VP extending from (3+), front contact 46 of relay 3V, back contact 41 of relay 4V, lower Winding of relay VP and front contact I4 of relay FP to (CN). Relay VP closes its above described stick circuit by way Relay E of its front contact 52. Relay E is now picked up over a circuit extending from front con tact 48 of relay CK, back contact (iii of relay 4V, front contact 6! of relay 3V, front contact 64 of relay VP and upper winding of relay E to The opening of back contact 23 of relay E deenergizes the line circuit.

This marks the beginning of the third off period which drops relay FP. A circuit is now closed for picking up relay 3V which extends from front contact 12 of relay SA, back contact [3 of relay FP, front contact ll of relay VP, front contact i9 of relay 3V and winding of relay 4V to Relay W closes an obvious stick circuit for itself at its front contact 5 Relay E is now de-energized because the above described circuit including its upper winding is open at back contact of relay dV. The closing of back contact 23 of relay E energizes the line circuit.

This marks the beginning of the fourth on period which picks up relay FP. Relay VP is now de-energized by means of a circuit extending from (B), front contact iii of relay VP, front contact 41 of relay lV, lower winding of relay VP and front contact M of relay F? to (CN). Relay E is now picked up over a circuit extending from front contact 48 of relay CK, front contact 68 of relay 3V, back contact of relay VP and lower winding of relay E to The opening of back contact 23 of relay E deenergizes the line circuit.

This marks the beginning of the fourth off period which drops relay FP. A circuit is now closed for picking up relay LV extending from front contact l2 of relay SA, back contact l3 of relay FP, back contact ll of relay VP, front contact E8 of relay 4V and Winding of relay LV to Relay LV closes an obvious stick circuit for itself at its front contact The opening of back contact 5! of relay LV de energizes the stick circuit of relay STR and this latter relay is released.

Since relay LV does not de-energize the above described pick up circuit for relay E, this relay remains picked up for a comparatively long interval of time and since the line circuit cannot be energized with relay E picked up, relay FP remains down for a comparatively long interval of time so that relay SA drops away. The dropping of relay SA de-energizes the stick circuits of all stepping relays and these relays are released. Relay E is de-energized when all stepping relays are restored to their normal positions.

The dropping of relay E again energizes the line circuit which results in picking up relay FP. Relay SA cannot be energized at this time, since its pick up circuit is open at back contact 40 of relay FF and its stick circuit is open at front contact d2 of relay SA. Relay SAP is de-energized by the opening of front contact $3 of relay SA and the opening of back contact 40 of relay FP. Relay CK is de-energized by means of a circuit extending from (B), front contact ll of relay CK, contact 28 of relay F in its left hand position, back contact 29 of relay SA and upper winding of relay CK to (CN). Since the current flow through the upper winding is in the opposite direction to that indicated by the arrow, the two windings oppose with the result that relay CK releases.

As above mentioned, the field station stepping bank steps through the cycle in a similar manner to that described in connection with the control ofiice. Relay SA is-dropped when contact I25 of relay FP remains down for the long time interval. Immediately after the end of this last long offperiod, the picking up of relay FP deeenergizes relay SAP at back contact I25, so that this relay is daenergized. Relay CK is de-energized when the normal current is applied to the line circuit for positioning relay F to the left, over a circuit extending from (B), front contact l3! of relay CK contact I22 of relay F in its left hand position, back contact N3 of relay SA and upper winding of relay CK? to (CN). This circuit is effective to de-energize relay CK by means of the differential action of the windings.

Polarity selection of controZ impulses-Assuming that the stepping relays pick up as above described, the first impulse applied to the line circuit (after the initiating impulse) is determined by the connectionof code jumper 66. For example, with jumper 66 connected to (B-) as shown in Fig. 2A the first impulse applied to the line circuit is as determined by relay D being positioned to the left over a circuit extending from (B), jumper 6E, front contact 6! of relay CD, front contact 30 of relay IV, back contacts 3!, 32, 33, and 34 of relays 2V, 3V, 4V and LV respectively, front contact 24 of relay STR, and winding of relay D to (CN) With contact 29 of relay D in its left hand position a impulse is applied to the line circuit during the first on period.

In the event that jumper 66 is connected in its alternate position to (B+), then the above described circuit would energize relay D to its right hand dotted position for applying a impulse to the line circuit for the first on period. Similarly, if the system is of sufficient size additional'stepping relays such as 2V, 3V and the like will select additional code jumper connections through contacts of the CD relay for providing combinations of and impulses in the line circuit on additional steps of the cycle. It is believed that the typical example illustrated is sufficient to indicate how this selection is made.

When the system takes its second step, relay 2V extends control bus C'IL through front contact 68 of relay CD to switch machine lever SML. If the contacts of lever SML are in a right hand position as shown in Fig. 2A, (B+) is applied to the winding of relay D which positions this relay to the right for'applying a impulse tothe line circuit at the second step. In the eventthat contact T2 of lever SML is in its left hand dotted position, then (B) is: connected to the winding of relay D which positions this relay to the left for applying a impulse to the line circuit on the second step. When the system takes additional steps of the cycle, relays 3V and 4V extend the circuit of relay D by way of'front contacts of relay CD to other controlling devices, such as a signal lever, which have not been shown but the operation of which will be obvious from the above typical example. i

From the above it will be observed that dif-..

ferent code combinations comprising a choice of two per step may be used for selecting field stations and for controlling devices thereat. The choice is or for each step, as determined by the: code jumper connections. and the control lever positions.

Transmission of controls-It will be assumed that relay lV at the station illustrated in Fig. 3 is picked up in synchronism with relay IV in the control ofiice. The impulse applied to the line circuit on the first step actuates the contacts of relay F to the left. A circuit is now closed for actuating the contact of relay IPT to the left extending from (B-), front contact I3! of relay CK contact I22 of relay F in its left hand position, front contact I23 of relay SA front contact I32 of relay CK control bus: CTL back contacts I33, I34 and I35 of relays 4V 3V and 2V respectively, front contact l35 of relay IV and winding of relay IPT to (CN).

It will be understood that the transmission of a impulse at the first step positions contact I22 of relay F to the right which applies (B+) to the winding of relay IPT for positioning this relay to the right. Thus a choice of two selections is obtained on the first step for positioning relay IPT to either of its two positions.

Relay 2V is picked up between the first and the second on periods so that a circuit is closed during the second on period for positioning relay SMR to the right. This circuit extends from (B+) contact I22 of relay F in its right hand dotted position (because lever SlVlL caused a impulse to be applied to the line on the second step), front contact I23 of relay SA front contact I32 of relay (3K back contacts I33 and I34 of relays 4V and 3V respectively, front contact I35 of relay 2V contact I31 of relay IP'lT in its left hand dotted position and winding of relay SM'R to (CN). Relay SMR actuates its. con tact I38 to the right for causing the switch machine to actuate the track switch to its normal position.

In the event that the second impulse in the line circuit is as determined by lever SML being in its reverse (left hand dotted) position, then relay F is actuated to the left for actuating relay SMR to its left hand dotted position, which closes a circuit from (B-) at contact I38 for positioning the track switch to its reverse position.

The transmission of additional controls is effective on succeeding steps of the stepping relay bank at the field station for selectively positioning other control relays similar to relay SMR the detailed circuits of which need not be shown for an understanding of the present invention.

With the release of relays SA and SAP at the field station, the stick circuits of the stepping relays are deenergized so that these relays are restored to their normal positions. Relay IPT and relay SMR remain in their last actuated positions until shifted by the reception of a succeeding code.

Automatic start.The system may be initiated into a cycle of operations from its normal condition by an automatic change in condition at a field station. Such an initiation may be due to a change in traffic conditions or to the operation of a traffic controlling device to anew position in response to controls received from the control office.

Such change in condition at the field station illustrated in Fig. 3, for example, drops relay CH which closes a circuit for picking up relay L0 extending from back contact I39 of relay CH back contact l29 of relay SAP back contact I4I of relay 0K and lower winding of relay L0 to Relay L0 closes a circuit for picking up relay PL extending from back contacts I43,

and VP respectively, back contact I48 of relay P winding of relay PL and front contact I49 of relay L0 to The picking up of relay PL de-energizes. the line circuit at back contact I40. It will be noted that the picking up of contact I20 of relay LO shifts the closed circuit of the stepping line from its back contact, which leads through other field stations, to common line Ill by way of resistance units R R and back contact I43 of relay PD.

The de-energization of the line circuit drops line relays F and F which in turn drop their associated FP relays. The dropping of relay FP .at the station closes a circuit for picking up relay SA which extends from back contact I25 of relay FP back contact I26 of relay SAP and winding of relay SA to The picking up of relay SA closes a circuit at its front contact I28 for energizing relay SAP The dropping of relay FP in the control oflice effects the picking up of relays SA and SAP in the manner described in connection with the initiation of a control cycle. Relay C is picked up when relay FP closes. its back contact 35 and relay C sticks until relay SAP is picked up, after which it drops in the manner described in connection with a control cycle. Thus, the opening of back contact 2i of relay C keeps the line circuit open in the control ofiice until after relay SAP has picked up, although this line circuit may be closed at the initiating station before relay SAP is picked up as will now be described.

The picking up of relay SA while relay FP is de-energized causes the picking up of relay IV over a circuit which is similar to the circuit in the control oflice which causes the picking up of relay IV. The picking up of relay IV de-energizes relay PL at back contact I46, so that the line circuit at the initiating field station is closed at back contact I40 of relay PL When relay 0 in the control office closes its contact 2I, the line circuit is energized to mark the beginning of the first on period and the system will step through the cycle as previously described in connection with the transmission of controls. Relay L0 remains stuck up during the cycle over a circuit extending from front contact I51 of relay SA front contact M2 and winding of relay L0 to Relay CK in the control office is not picked up during a cycle of this class. because relay F does not actuate its contact 28 to its right hand dotted position before relay SA opens its back contact 29. Relay STR is not picked up during a cycle of this class because relay CD does not pick up to close its front contact 2'! before relay SA opens its back contact I2. With relay CK down, its back contact I3 places a shunt around back contact 23 of relay E so that relay E is not effective to impulse the line circuit during an indication cycle. As will be later described the normal impulse periods (short) of such a cycle are provided by the field station while the long impulse periods are provided by relay EP in the control office.

Since relay STR is not picked up during a cycle of this class, relay D remains actuated to the left for transmitting a series of impulses throughout the cycle. Such a series of all impulses corresponds to a phantom code and does not result in the selection of any station for controls.

It will be understood that other field stations located between the station which is transmitting and the control office will also step through the indication cycle but, since their lockout relays are not picked up, their circuits are ineffective to cause the operation of relays corresponding to PL P and HR. Since the line circuit outward from the transmitting station is open at back contact I20 of relay L0 the line relays at the outward stations will remain down throughout the indication cycle. This results in the FP relays at these stations dropping their contacts for closing circuits which pick up their associated SA relays. The SA relays at these stations close circuits for picking up their associated SAP relays. The SAP relays stick over circuits similar to that extending through back contact I25 of relay FP and front contact I26 of relay SAP Since the FP relays are not intermittently operated, their'front contacts similar to I25 are not closed for energizing the SA relays and since the back contacts similar to I26 of relay SAP are open the SA relays drop out. In brief the SA relays are dropped and the SAP relays are stuck up at the stations on the line beyond the transmitting station.

The first stepping relay at these stations will likewise be picked up upon the response of the corresponding SA relays but will drop again following its release. Therefore these distant stations remain in the condition with their F and FP relays down and the SAP relay picked up until the end of the cycle at which time the line againis energized. At this time the F and PP relays pick up which de-energizes the circuits of the SAP relays extending through their front contacts similar to I26.

Transmission of indications.When relay L0 at the calling station (illustrated in Fig. 3) is picked up, the line circuit will be de-energized to mark the end of the first on period by the picking up of relay PL over a circuit extending from back contacts I43, l44and I45 of relays 4V 3V and 2V respectively, front contact I 46 of relay IV front contact I41 of relay VP back contact I48 of relay P winding of relay PL and front contact I49 of relay L0 to This is a short impulse, terminated at the field station by the picking up of relay PL and is of such a duration that relay E in the controlofiice does not remain picked up for a sufiicient period of time to allow relay EP to drop. Therefore this indication is executed by closing a circuit for actuating relay IPT to its left hand dotted position, which circuit extends from (B), front contact 80 of relay E, front contact 8! of relay EP, length of time indication bus L'II back contact 82 of relay CK, back contact 83 of relay FP, front contact 84 of relay VP, back contact 85- of relay 3V, front contact 86 of relay IV and Winding of relay IPT to (CN).

The alternate indication condition is provided on the first stepwhen jumper I50 at the field station is connected in its dotted line position to This closes a circuit from jumper I50, front contact ISI of relay IV back contacts.

of relay EP de-energizes the line at its front.

contact 22 so that the system takes its nextstep. This indication condition. is executed by positioning relay IPT to the right over the previously described circuit, which now extends ;from-(B+) at back contact M of relayEP. During an in--' dicationcycle, relay CK is down and the (+9 for operating relay E is supplied from back contact 99 of relay LV.

The above example indicates how the two indication conditions controlled by the length of animpulse are obtained. It will be obvious that these two conditions of the line circuit can be obtained at. additional steps of the cycle in a similar ,manner'when the system is of such a size as to warrant additional code jumpers similar to I50. It will be noted thatcontacts I43, I44, I45, I46; and I4] of the stepping relay bank at the fieldstation are so arranged that a selective circuit is made up for relay PL to terminate the impulse period of each step, provided back contact I48 of. relay P is closed. Since relay P is controlled in accordance with a selection of two conditions, it will be apparent that the calling field station can terminate each impulse period by de-en'ergizing the line circuit, or it can leave the line circuit energized at the field station and wait until the control ofiice terminates an impulse period, which latter condition results in. a long impulse.

It will now be explained how the strength of current indication condition is effected. When relay. IV at the calling station is picked up and with code jumper I60 in the position shown, relay I-IL remains down so that the line circuit is energized in series with resistance unit R This line circuit alsoincludes resistance unit R for the purpose of compensating for the resistance of the line extending outward from the calling station, which is removed when relay L0 is picked up. With resistance R included in the line circuit, a comparatively weak current flows which is insufiicient to pick up relay HL in the control office. This condition is executed in the control ofiice over a circuit extending from (B) back contact I4 of relay HL, strength of current indication bus SCI, back contact 50 of relay CK, front contact 15 of relay FP, back contacts 16, TI and I8 of relays 4V, 3V and 2V respectively, front contact I9-of relay IV and winding of relay ZPT to (CN). Current flow in this circuit is effective to position the contacts of relay ZPT to the left.

In the event that jumper I66 of Fig. 3 is connected in its dotted line position to then relay HL is picked up for short circuiting resistance R at its front contact I30. This allows a comparatively strong current to flow over the line circuit which picks up relay HL. Relay HL closes its front contact 69 which short circuits its lower winding to render this relay slightly slow in releasing, for the purpose of maintaining its front contact I4 closed until after relay FP drops its .front contact 15 at the termination of the impulse period. This impulse condition is executed by connecting (13+) at front contact I4 of relay HL over the above described circuit to the winding of relay 2PT. which positions this relay to the right.

It is believed that the above typical example indicateshow achoice of two indications are obtained by iinpulsing the linecircuit With weak or strong impulses. These two indication conditions, plus the .two previously described length of time indications, provide a choice of four indication:conditions for'each step of the cycle.

With relays IPT and 2PT positioned to the left, .a circuit is .closed. for picking up relay IST after relay. 2V. isvoperated, which circuit extends from back contact 87 of relay CK, front contact-880i relay 2V, front contact 89 of relay F15, contact 90 of relay IPT in its left hand dottedposition, Contact SI of relay ZPT in its left hand dotted position and winding of relay IST .to Relay lST closes a stick circuit for itself extending from back contact 8'! of relay CK, front contact 88 of relay 2V, front contact 92 and winding of relay IST to This stick circuit maintains relay IST picked up until the end of the cycle, when relay 2V opens its contact 88.

It will be understood that four difierent combinations of relays IPT and 2PT are obtained on the first step in accordance with the four indication conditions above described. All of these four different combinations can be used for selecting individual station relays, one of which is indicated by the selection of relay HST. Another is obtained by relay IPT positioned to the right and relay 2PT positioned to the right for one combination. Relay IPT positioned to the left and relay 2PT positioned to the right is for another combination. Still another combination is with relay IPT to the right and ZPT to the left.

It will be obvious that additional steps of the cycle may be used for positioning additional pilot relays, so that 16 combinations may be obtained on two steps, etc.

Indications from registered stati0n.-When the line circuit is energized, after the station has been registered in the control office as above described, indication storing relays such as relays IIR and 21R of Fig. 2B are selectively actuated in accordance with the positions of relays at the calling station, such as relays WP and T of Fig. 3.

For example, with relay T energized the second impulse of the cycle is a weak impulse because there is no circuit completed for picking up relay EU to short circuit resistance unit R This results in relay HL remaining down so that a circuit is closed for positioning relay IIR to the left, which circuit extends from (B), back contacts M and 5B of relays HL and CK respectively, front contact 15 of relay FP, back contacts 76 and H of relays 4V and 3V respectively, front contact 18 of relay 2V, front contact 93 of relay IST and winding of relay IIR to (ON). Relay IIR may have its contacts arranged to de-energize a track occupancy lamp under this condition.

If relay T is de-energized, then relay HL is picked upover an obvious circuit including back contact I56 of relay T This results in short circuiting resistance unit R for picking up relay HL on this step, so that relay IIR is actuated to the right over the above described circuit which now extends from (B+) at front contact M of relay l-IL. Relay IIR may have its contacts arranged to energize a track occupancy lamp when it is positioned to the right.

A choice of two other codes can be transmitted on this same step, which for example has been shown in connection with relay WP With this relay picked up there is no circuit for energizing relay P 'therefore relay PL picks up and de-energizes the line before the control oflice deenergizes it. This prevents the dropping of relay EP in the control oflice. A circuit is closed for positioning relay 21R. to the left which extends from (B-), front contact 80 of relay E, front contact 8! of relay EP, back contact 82 of relay CK, back contact 83 of relay FP, back contact 84 of relay VP, back contact 94 of relay 4V, front contact 95 of relay 2V, front contact 96 of relay [ST and winding of relay 21R to (CN). Relay 21R may have its contacts arranged to energize switch machine indication lamps when in this position.

In the event that the switch machine is unlooked, a circuit through back contact I66 of relay WP is effective to pick up relay P for preventing relay PL picking up and de-energizing the line at the field station. This means that the line will remain energized until relay EP oleenergizes it in the control ofiice. This closes an executing circuit for actuating relay HR to the right, which circuit is the same as previously described except that it now extends from (3+) at back contact 8! at relay EP. With relay 21R positioned to the right, switch machine indicating lamps may be de-energized for indicating that the track switch is in its unlocked condition.

It will be obvious that other indications may be transmitted, such as signals clear and signals at stop in the same manner described in connection with the switch machine. It is therefore believed unnecessary to continue the dc scription for additional steps of the cycle, since these additional steps effect the transmission of indications in a manner similar to that already described.

Pluralz'ty of stored start conditions.In the event of several stored oliice and field start conditions, the system functions to send controls until all stored controls have been taken care of. After this the system is used for the transmission of indications on separate cycles until all indications have been taken care of. Assuming that there are more than one stored office and field start conditions, there will be more than one storing relay in the control office picked up, so that when relay CD of Fig. 2A is dropped at the end of a cycle a similar relay is picked up to close a circuit similar to that extending from front contact 21 of relay CD, lower winding of relay STR and back contact E2 of relay SA to This picks up start relay STR for establishing the above described circuit from (B+) at back contact 30 of relay lV (when all stepping relays have dropped), to relay D for positioning contact 28 of this relay to the right. This is effective to initially energize the line circuit with a impulse which marks the succeeding cycle as one for the transmission of controls.

The field stations with stored start conditions have their CH relays dropped butthe circuits are not completed for picking up the lookout relays at the stations, because under this condition the SAP relays at the stations do not drop their contacts similar to I29 for completing the circuits to the lookout relays. This is because the dropping of relay SA in the control oifice allows a control start condition to be established as above pointed out, before the SAPrelays at the stations are dropped and since this control start condition is effective to energize the line with a impulse, the checking relays similar to relay CK are picked up which also opens the circuits of the lookout relays at back contacts similar to Hll. Therefore, as long as stored oflice start conditions exist the system will continue operating through cycles for the transmission of controls without allowing a field station to break in until all controls have been taken care of.

The communication system functions as abov described to transmit the proper controls as determined by the particular CD relay which is picked up. Should there be a plurality of field stations with indications to transmit when there I winding of relay L to are no controls awaiting transmission, these stations transmit their indications in rotation with the station nearest the office having preference.

Lockout between field s tations.Assuming that two change relays are dropped at approximately the same time, the corresponding LO relays Will be picked up. Assuming that the station illustrated in Fig. 3 is one of the two having indications ready for transmission at approximately the same time, it will be noted that the opening of back contact I26] of relay LO prevents the energization of the line circuit outward from the station illustrated in Fig. 3.

The picking up of relay L0 energizes the'line inward towards the control office, since the continuity of the line is established through front contact I20 of relay L0 resistance units R and R and back contact I40 of relay PL This closed circuit is immediately interrupted however because relay PL picks up over the previously described circuit including front contact I49 of relay L0 This de-energizes the line for initiating the system, as previously described in connection with an indication cycle. Relays F FP F and FF are dropped and relays SA IV SAP SA, SAP and IV are picked up as previously described. Relay C is also picked up and dropped and when its back contact 2I is closed, back contact I40 of relay PL will be closed so that the line circuit is again energized.

The picking up of relay SA closes a stick circuit for relay LO extending from front contact I57 of relay SA front contact I42 and Therefore relay L0 remains stuck up throughout the cycle and at its front contacts I49, I55 and I65 the indication conditioning circuits are completed as above described.

At the station farther out the line attempting to transmit, the line relay and line repeating relay are dropped which picks up the SA and SAP relays in sequence. As soon as the SAP relay at this inferior station is picked up, the pick up circuit of the SA relay is opened at a back contact similar to I26 and since the FP relay is down, the stick circuit of the SA relay is open at a front contact similar to I25. This results in the SA relay dropping its contacts, so that there is no stick circuit for holding the lookout relay at a front contact similar to I and since the pick up circuit of the lock out relay is open at a back contact similar to I29, this relay is dropped. At the end of the cycle, when the line circuit is again energized the F, FP and SAP relays at the inferior station are restored to normal as already described in connection with the description of an indication cycle. At the inferior station, when the SAP relay closes its contact similar to I29 this station can obtain control of the communication system, provided no other, superior station is waiting with a stored start condition.

In connection with field start conditions which occur in sequence, it will be noted that the dead line for picking up a lookout relay is at the time when the SAP relay opens its back contact I29. Therefore, any station which initiates a cycle sufficiently in advance of a changed condition occurring at another station for the first station to pick up its SAP relay, will obtain access. to the communication system and lockout all other stations. It is believed that the above example relating to two simultaneous start conditions and the statement regarding sequential starting conditions are sufficient to convey a proper understanding ofthe' lockout feature of the present invention.

Having thus described one specific embodiment of a centralized traffic controlling system, it is desired to be understood that the particular arrangements illustrated and suggested are only typical of applicants invention and are not intended to indicate the exact circuit design and specific arrangement necessary to carry out the features of the invention. This particular formhas been illustrated to facilitate in the disclosure, rather than to limit the number of forms which the invention may assume and it is further desired to be understood that various modifications may be made in order to meet the various problems encountered in practice, the system may be varied in the number of field stations to which the invention is app-lied and the amount of apparatus at each field station may be varied to suit local conditions, all without in any manner departing from the spirit or scope of the present invention, except as limited by the appended claims.

-What I claim is:

1. In a centralized traflic controlling system, a plurality of locations including a control oflice and a plurality of field stations connected by a line circuit, control transmitting means in said office for intermittently and reversibly energizing said line circuit during an operating cycle of said system from a source of current at said ofiice for providing a first series of polar impulses, indication transmitting means at each of said stations for intermittently and distinctively energizing said line circuit during an operating cycle of said system from said source of current for providing a second series of distinctive impulses, means at said office for selecting the polarity of each of said first series of impulses in accordance with predetermined codes, means at said stations responsive only to said first series of impulses, means at said ofiice responsive only to said second series of impulses, and means for rendering said control transmitting means superior to said indication transmitting means.

2. In a centralized traffic controlling system; a control office and a plurality of field stations connected by a line circuit; means for intermittently energizing said line circuit from a source of current for providing series of impulses; means at said ofiice for causing the impulses of one series to be of a first and a second character to characterize a control code; means at said ofiice for causing each of the impulses of another series to be of said first character to characterize a noncontrol code; means at each of said stations for characterizing the impulses of said another series as to constitute impulses of a third or fourth character to characterize an indication code; and means for preventing the energization of said line circuit with an impulse of said fourth character during a control code series in which said line circuit is energized with impulses of said first and second characters.

3. In a centralized traific controlling system, a control ofiice and a plurality of field stations connected by a line circuit, means for transmitting a plurality of series of current impulses of Variable polarity in one direction over said line circuit, means for transmitting a plurality of series of current impulses of variable length and variable strength in another direction over said line circuit, and means for preventing the transmission of a series of variable length and variable strength impulses as long as a condition exists requiring the transmission of variable polarity impulses.

4. In a remote control system, a line circuit over which .a plurality of series of impulses are transmitted, a line relay at each end of said line circuit responsive to said impulses, an impulsing relay and a timing relay at the impulse transmitting end of said line circuit, means rendering said impulsing relay effective to transmit said plurality of series of impulses, means rendering said timing relay ineffective to time the impulses of a first series, means responsive to the impulses and including the line relay at the transmitting end of said line circuit for timing the impulses of said first series, and means including the line relay at the receiving end of said line circuit for rendering said timing relay effective or ineffective to time said impulses of a second series.

5. In a remote control system, a line circuit over which a plurality of series of impulses are transmitted, a line relay at each end of said line circuit responsive to said impulses, an impulsing relay and a timing relay at the impulse transmitting end of said line circuit, means rendering said impulsing relay effective to transmit said plurality of series of impulses, means rendering said timing relay ineffective to time the impulses of a first series, means responsive to the impulses and including the line relay at the transmitting end of said line circuit for timing the impulses of said first series, means including the line relay at the receiving end of said line circuit for ren dering said timing relay effective or ineffective to time said impulses of a second series, and means controlled by the line relay at the transmitting end of said line circuit for registering the lengths of the impulses of said second series.

6. In a remote control system; a line circuit; a line relay connected to said line circuit; means for energizing said line circuit with a first series of time spaced impulses of current of normally short and abnormally long lengths, whereby said line relay is intermittently operated and released; a slow release relay; means including said line relay for maintaining said slow release relay picked up as long as said impulses are normally short and for releasing said slow release relay when any one of said impulses is abnormally long; means controlled by the release of said slow release relay for rendering an impulse abnormally long; and additional means for maintaining said slow release relay picked up irrespective of the length of the impulses, whereby a second series of all normally short impulses is applied to said line circuit.

'7. In a remote control system; a line circuit; a line relay connected to said line circuit; means for energizing said line circuit with a first series of time spaced impulses of current of normally short and abnormally long lengths, whereby said line relay is intermittently operated and released; a slow release relay; means including said line relay for maintaining said slow release relay picked up as long as said impulses are normally short and for releasing said slow release relay when any one of said impulses is abnormally long; means controlled by the release of said slow release relay for rendering an impulse of said abnormal time interval; additional means for maintaining said slow release relay picked up irrespective of the length of the impulses, whereby a second series of all normally short impulses is applied to said line circuit; and means controlled by said slow release relay for registering said normal and abnormal time interval impulses.

8. In a remote control system; a transmitting station and a receiving station connected by a line circuit; means at said transmitting station for applying a first and a second series of spaced impulses of current to said line circuit; impulse receiving relay actuated from one position to another in response to said impulses; a normally energized and picked up slow release relay for opening said line circuit when deenergized; means controlled by said impulse receiving relay, and effective if it remains in said another position for more than a predetermined time interval, for releasing said slow release relay to cause each impulse to be rendered normally long; a series of polar indication relays, one for each impulse of said first series; means rendered effective each time said impulse receiving relay is actuated to said one position for energizing one of said indication relays to one position provided said slow release relay is then picked up and to another position provided said slow release relay is then released; means at said receiving station for at times opening said line circuit to cause said impulses to be abnormally short, whereby said impulse receiving relay is actuated to said another position for a time less than said predetermined time interval; and additional means at said transmitting station for maintaining said slow release relay picked up throughout said second series of impulses and for causing said second series of impulses to be invariably normally short.

9. In a code communication system for transmitting controls from a control office to a field station and for transmitting indications from the field station to the control office, a line: circuit including a source of energy at the control office and connecting the control office and the field station, transmitting means at the control office effective when initiated to energize said line circuit from said source with a series of time spaced impulses, each having a selected polarity, means for energizing said line circuit from said source with one polarity when said office transmitting means is inactive, transmitting means at the field station effective when initiated to cause the opening and closing of the line circuit for relatively long and short periods of time to form successive series of time spaced impulses, means for initiating said transmitting means at the field station only if the line circuit is energized with said one polarity and only if said control office transmitting means is inactive, means at the control office for applying the opposite polarity to the line circuit at the end of any series of V impulses transmitted from the field station, and means for initiating said transmitting means at the control office when said opposite polarity is applied, whereby the transmitting means at the control ofiice can interrupt the transmitting means at the field station at the end of any series of impulses effected by the field station.

10. In a code type communication system; a line circuit connecting a control office and a field station and including a source of energy at the control office; a transmitter at the control office effective, when set into operation, to energize said line circuit with a series of time spaced impulses of polarities selected in accordance with controls to be transmitted; a transmitter at the field station effective when set into operation to open and close said line circuit for a series of relatively short and long time periods in accordance with indications to be transmitted; initiating means at the control office for setting said transmitter at the control office into operation when such initiating means is rendered active; manually operable starting means in the control oifice for rendering said initiating means active; means at the control office for energizing said line circuit with a particular polarity when said initiating means is inactive and for energizing it With the opposite polarity when said initiating means is rendered active; a changeable device at the field station; initiating means at the field station for setting the transmitter at its station into operation when such initiating means is rendered active; and circuit means effective upon a change in said device, only if said line circuit is energized with said particular polarity, to render said initiating means at the station active.

11. In a code communication system of the character described for transmitting controls from a control oifice to a field station and for transmitting indications from the field station to the control ofiice, a line circuit connecting the control office and the field station, a source of energy at the control office, a transmitter at the control ofiice operable to energize said line circuit from said source with different series of time spaced impulses only if the field transmitter is inactive, each of said impulses being of one selected polarity or the other in accordance with a code, means for energizing said line circuit from said source with a particular polarity when said ofiice transmitter is inactive, a transmitter at the field station operable to open and close the line circuit for relatively long and short periods of time to efiect the energization of the line circuit with successive series of long and short time spaced impulses, only if said transmitter at the control ofiice is inactive and said line circuit is energized with said particular polarity, and means at the control oifice for rendering said transmitter at the field station inactive at the end of any series of impulses transmitted from the field station to allow the operation of said transmitter at the control ofiice by applying a polarity different from said particular polarity, whereby the transmission of controls from the control oifice is given superiority over the transmission of indications from the field station.

12. In a system of code communication between a control oflice and a plurality of field stations, a single line circuit connecting the control ofiice and the several field stations, a source of energy at the control ofiice cycle marking means in the control ofiice and at each field station assuming its normal condition at the end of an operating cycle in response to a prolonged deenergization of said line circuit, manually operable starting means in the control oifice for initiating an opcrating cycle for the transmission of controls, means in the control ofiice including said source for energizing said line circuit with one polarity whilethe system is at rest and responding to operation of said manual starting means to change the energization of the line circuit to the other polarity, and equipment at each field station comprising, a changeable device having different conditions to be indicated in the control ofiice, sectionalizing, means responsive to a change of condition of said device for terminating said line circuit at the corresponding station, means responsive to the energization of said line circuit with said other polarity prior to the energization of said cycle marking means for preventing operation of said sectionalizing means, a code transmitter, and means responsive to the flow of current in said line circuit in the corresponding station after operation of said sectionalizing means for rendering the code transmitter at that station effective during the ensuing cycle to open and close said line circuit to form an indication code characteristic of the station.

13. In a remote control system; a line circuit connecting a control oflice and a field station; a control ofiice line relay and a field station line relay connected in series in said line circuit; means at thecontrol ofiice including a source of energy for initially energizing said line circuit; transmitting means at the field station operating, when active, in response to each energization of said line relay for opening said line circuit after a short period of time and then re-closing the line circuit or operating to leave it closed until the next impulse period; a slow release relay at the control ofiice; means responsive to each energization of said control oflice line relay for maintaining said slow release relay picked up for each short impulse period but allowing it to drop away for an abnormally long impulse period; means including said slow release relay for terminating an abnormally long impulse period and then reclosing the line circuit; whereby said line circuit is energized with impulses of normal and abnormal length as determined by said transmitting means at the field station; cycle checking means at the control office and at the field station acting at times to render said transmitting means at the field station inactive to maintain said line circuit closed and for maintaining said slow release relay at the control oifice picked up irrespective of the length of the impulses on said line circuit; and means at the control ofiice operating when said cycle checking means is active to impress impulses or normally short time periods on said line circuit.

DARROL F. DE LONG. 

